Dynamic treatment system and method of use

ABSTRACT

A system and method are provided for monitoring the condition of the skeletal system and adjusting a treatment device to provide appropriate treatment in response to the sensed signal. More particularly, in one aspect the present invention is directed to a sensor for detecting changes at a spinal level and a dynamic treatment system adjustable in response to the detected changes.

FIELD OF THE INVENTION

The present invention is directed to improved instrumentation andmethods for monitoring the condition of the skeletal system andproviding appropriate treatment. More particularly, in one aspect thepresent invention is directed to a sensor for detecting changes at askeletal segment and a dynamic treatment system adjustable in responseto the detected changes.

BACKGROUND OF THE INVENTION

The present invention relates to sensing changes in tissues associatedwith a skeletal system and adjusting the treatment being administered tothe patient in response to the sensed changes. Treatments of theskeletal system are typically static once a device is surgicallyimplanted. However, individual patient's often experience unexpectedchanges during healing or as a result of the initial treatments. Beingable to detect the onset of these changes in the skeletal environmentmay allow early medical intervention to treat the condition, stop itsadvance or slow the progression. However, it is currently difficult tomonitor the condition of the anatomic structures adjacent a joint, suchas a spinal segment or knee. Thus, there is a need for a device andsystem that is able to monitor the skeletal system environment, sensechanges that are indicators of potential problems and adjust thetreatment the patient is receiving.

Therefore, there remains a need for improved instrumentation and methodsfor evaluating the condition of a portion of the skeletal system andadjusting the treatment being administered to the patient in response tothe sensed changes in condition.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a system for treating aportion of the skeletal system within a patient. In one form, the systemcomprises a sensor having a sensing portion implantable in the bodyadjacent to the portion of the skeletal system, with the sensing portiongenerating a sensor signal in response to a sensed characteristic of theskeletal system; and a dynamic treatment system having at least a firsttreatment mode and a second treatment mode. In one aspect, the treatmentsystem is in communication with the sensor and responsive to the sensorsignal to adjust the treatment system from the first treatment mode tothe second treatment mode. In one form, the dynamic spinal treatmentsystem includes mechanical stabilization of the skeletal system that isadjustable from a first mode to a second mode. In another form, thedynamic treatment system includes at least first treatment compound.

In still a further aspect, the present invention provides a method oftreating a portion of the skeletal system in a patient. In one form, themethod comprises providing a sensor configured for implantation in thebody adjacent a portion of the skeletal system and a dynamic treatmentsystem configured for communication with the sensor. The sensor anddynamic treatment system are implanted in the body adjacent the portionof a skeletal system with the dynamic treatment system in a firsttreatment mode. The method continues with sensing characteristics of theskeletal system with the sensor, sending a sensor signal to the dynamictreatment system, and adjusting the dynamic treatment system to a secondtreatment mode in response to sensor signal.

Further aspects, forms, embodiments, objects, features, benefits, andadvantages of the present invention shall become apparent from thedetailed drawings and descriptions provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of implantable sensors located adjacent the discspaces in the spinal column according to one aspect of the presentinvention.

FIG. 2 is a side view of implantable sensors located in the vertebralbodies of the spinal column according to another aspect of the presentinvention.

FIG. 3 is a schematic illustration of the wireless implantable sensor ofFIG. 1.

FIG. 4 is a flow chart illustrating use of the implantable sensor andexternal receiver of FIG. 1.

FIG. 5 is a side view of a hand held sensor according to another aspectof the present invention.

FIG. 6 is a side view of a series of sensors according to another aspectof the present invention.

FIG. 7 is a side view of a spinal fixation system for dynamicstabilization in association with implantable sensors according toanother aspect of the present invention.

FIG. 8 is a schematic view of the dynamic controller of thestabilization system of FIG. 7.

FIG. 9 is a side view of a sensor and a treatment compound dispenser inaccordance with another aspect of the present invention.

FIG. 10 is a flow chart illustrating use of an implantable sensor incombination with a treatment device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of thepresent invention, reference will now be made to the embodimentsillustrated in the drawings, and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the invention is intended. Any alterations and furthermodifications in the described devices, instruments, methods, and anyfurther application of the principles of the invention as describedherein are contemplated as would normally occur to one skilled in theart to which the invention relates.

Referring now to FIG. 1, shown therein is an implantable sensor 100 formonitoring changes in tissue near the disc space area 20 disposed at thespinal level between vertebrae V1 and V2. FIG. 1 shows the implantablesensor unit 100 in wireless communication with an external device 200.In one aspect, the implantable sensor unit 100 is configured to detectand keep track of indicators associated with changes in tissue density.The implantable sensor unit 100 is also configured for wirelesscommunication with the external device 200. Similarly, the externaldevice 200 is configured for wireless communication with the implantablesensor unit 100. In particular, the external device 200 is adapted forretrieving, storing, and displaying, in human intelligible form, thetissue density data detected by the implantable sensor unit 100.

As discussed more fully below, although FIG. 1 illustrates use withinthe spinal column, it is fully contemplated that in other embodimentsthe sensor unit 100 may be utilized throughout the skeletal system. Forexample, but without limitation to other applications, in one embodimentthe sensor is placed adjacent the knee. In another embodiment, thesensor is placed adjacent the acetabular cup. In still a furtherembodiment, the sensor is placed to sense characteristics of a longbone. Moreover, when used with the spinal column, one or more sensorsmay be disposed at a plurality of locations adjacent the spinal levelincluding, but not limited to, within the disc space or attached to theannulus adjacent to the disc space. Still further, in another aspect theimplantable sensor 100 is affixed to bone of the skeletal system suchthat it may monitor the bone, adjacent soft tissues, such as muscles,nerves and connective tissues. Further, although not illustrated, theimplant may be within or integral to an artificial implant joined to theskeletal system, attached to an artificial implant, adjacent to anartificial implant, or any combination of these locations.

FIG. 2 shows the sensor unit 100 adapted for being disposed at leastpartially within a bone, vertebra V1. In the illustrated embodiment, theouter shell of the sensor unit 100 is substantially similar in shape andsize to a bone nail. However, sensor unit 100 may be of any shape orform adapted for placement within a portion of a bone such as vertebraV1. In an alternative embodiment, the sensor unit 100 is substantiallyshaped like a coin and adapted for placement within a portion of bone.

Referring to FIG. 3, the implantable sensor 100 includes a sensor 110, asignal processor 120, a memory unit 130, a telemetry circuit 140, and apower source 150. In one embodiment, the sensor 110 is an acoustictransducer responsive to acoustic signals transmitted through humantissue. While the implantable sensor unit 100 is described as having aseparate signal processor 120, it is filly contemplated that thefunction of the signal processor, described below, may be incorporatedinto either the sensor 110 or the memory 130, eliminating the need for aseparate signal processor. Similarly, it is fully contemplated that thefunctions of the various components of the sensor 100 may be combinedinto a single component or distributed among a plurality of components.Further, it is fully contemplated that the sensor 100 may include otherelectronics and components adapted for monitoring indicators of changesin tissue structure including deterioration and/or healing.

The telemetry circuit 140 is adapted for providing power to the acoustictransducer used as sensor 110 and transferring the detected indicatorsto an external device 200. It is contemplated that the telemetry circuitwill provide power to the acoustic transducer via inductive coupling orother known means of passive power supply. It is also contemplated thatthe external device 200 may be utilized to provide the power to thesensor unit 100 through direct inductive coupling. That is, the sensorunit 100 may be externally powered. Further, this allows the sensor unit100 to remain in a dormant state whenever an external power supply isnot available and then become active when the external power supply ispresent. In this manner, the sensor unit 100 does not require adedicated power supply such as a battery. This allows the sensor unit100 to be much smaller than would otherwise be possible with a dedicatedpower supply, which in turn allows placement of the sensor in morelocations without interfering with body mechanics or functions.

It is contemplated that the sensor is utilized to detect indicators oftissue density over regular intervals such as every day, every week,every month or every 6 months as determined by the treating physician.In this regard, it is contemplated that in one embodiment the patientreturns to a doctor's office for each reading. At such time the healthcare provider would place the external device 200 in the vicinity of thesensor unit 100. Through inductive coupling via the telemetry unit 140the sensor unit 100 would be powered by the external device 200. Thesensor 110 would then take a reading by detecting indicators of tissuedensity. This reading would then be relayed to the external device 200via the telemetry circuit 140. The reading may then be analyzed by thehealth care provider and appropriate medical treatment may be taken. Forexample, the health care provide may determine that adjustments to theinitial treatment course are needed and institute a second treatmentcourse for the patient. The process of evaluating patient progress basedon sensed changes in the tissue and changing the treatment coursecontinues until adequate patient relief is obtained. It is alsocontemplated that in another embodiment the patient obtains thesereadings without a need to go to the doctor's office. For example, thepatient is be provided with the external device 200 that is capable ofproviding power to the sensor unit 100, obtaining the readings, and thenrelaying the readings on to the doctor's office. For example, theexternal device transfers the readings to the doctors office via a phoneline or computer network. It is contemplated that a system similar tothat of Medtronic's CareLink may be utilized.

The implantable sensor unit 100 may fiction in a variety of ways. Underone approach the sensor unit 100 uses a type of comparative analysis todetermine changes in the tissue properties of the spinal segment. Thatis, an initial baseline or threshold range of signals will either bedetermined by the sensor itself or provided to the sensor by the healthcare provider. Then the sensor 100 will monitor the indicators of tissueproperties and when the signals detected are out the threshold range thesensor will store those signals in its memory 130. Then this data isextracted by the health care provider via external device 200. With thisdata the health care provider then chooses the appropriate treatmentplan. For example, the caretaker may choose to have the patient undergoadditional examinations such as a CT scan or an x-ray. Either based onthe additional examinations or other factors, the caretaker may insteador in addition choose to adjust the threshold range of the sensor.

It is fully contemplated that a treating health care provider may wantto change what the sensor considers the normal range of signalsovertime. For example, as an artificial implant, such as a artificialdisc replacement, is incorporated into the body the signals associatedwith tissue density near the bone-implant connection point will changeuntil the implant is fully integrated. Further the connective tissuebetween adjacent vertebral bodies will heal from the trauma of surgerywith changes to the connective tissue sensed by the sensor. Once theimplant is fully integrated, the normal range of signals from thebone-implant interface and other tissue in the spinal segment may beconsistent for a period of months or years. It is contemplated that thesensor 100 be programmable, self-learning, or both to adjust thethreshold levels to match the normal range after the healing process hasbeen substantially completed.

Self-learning implies that the sensor 100 is able to determine theproper range of signals by monitoring the signals over a period of timeand then via algorithms in its signal processing unit to decide on therange of signals indicative of normal tissue characteristics adjacentthe spinal segment. In this regard, it is fully contemplated that thehealth care provider may be able to override the determinations made bythe sensor 100 by programming in the thresholds or, on the other hand,the caretaker may reset the sensor's determinations and simply have thesensor recalculate the proper range based on current signals detected.Thus, as described above when an implant becomes fully integrated thecaretaker may decided to reset the self-learning sensor so that theranges are based on the signals associated with the fully integratedimplant.

In regards to setting the ranges, it is contemplated that in oneembodiment the patient is instructed through a series of movements suchas sitting down, standing up, walking, climbing stairs, or cycling withthe sensor 100 detecting the associated indicators of tissuecharacteristics such as for example, but without limitation to othersensed characteristics either alone or in combination with density,elasticity, size, inflammation, temperature, Ph, blood flow, pressure,electromyography (EMG) signals, and nutrient flow in the spinal segmentof interest. Based on the sensed signals, the sensor threshold rangesare set for operation. For example, the acoustic signals produced bythese and other movements are detected within a bone or other tissue ofthe skeletal system being monitored. Thus, instructing the patientthrough many of the normal motions and movements of everyday lifeprovides a good variety of signals that may be used to base the normalsignal range upon. Over time, the patient may again be put through asimilar series of movements to reset or recalibrate the sensor 100 asseen fit by the caretaker. Further, changes in detected characteristicsduring the series of movements may be used to diagnosis a patient'scondition based on comparing the sensed properties in one activity tothe sensed properties in a different activity or position.

Under another approach, the sensor 100 may fiction by monitoring forsignals associated with the onset of ligament tears, cartilage damage,annulus tears, annulus herniation, bulging discs or other changes intissue density or shape associated with moving joints. For example,there are certain acoustic sounds and vibrations associated withdegenerating conditions in the knee, hip, shoulder, jaw, elbow andspinal segments, including the intradiscal environment. In thisembodiment, the sensor 100 is configured to detect and recognize theseacoustic signals. For example, the sensor 100 utilizes various filters,amplifiers, and algorithms to remove background noise and focus on thedetection of the signals indicative of degenerating conditions in theintradiscal structures or other changes in tissue density. Though in thecurrently described embodiment the sensor 100 is an acoustic sensor, itis also contemplated, and described more fully in U.S. patentapplication Ser. No. 11/344,667 entitled IMPLANTABLE SENSOR, byDonofrio, et al., filed on Feb. 1, 2006 incorporated herein by referencein its entirety, that the sensor 100 may utilize a variety of sensingfeatures, including impedance, to detect changes in tissue density.

In the case of an acoustic sensor 110 as in one embodiment, the acoustictransducer is configured for detecting sounds and acoustic wavesindicative of tissue density. Under one approach if the detected signalexceeds the normal range of signals as determined by the signalprocessor 120, then the signal will be stored in the memory 130. In thisregard, the signal processor 120 is configured to determine theparameters or threshold levels of signal ranges for detection by thesensor 100. The signal processor 120 sets parameters such as theamplitude, frequency range, or decibel level required before a signal isconsidered an indication of a change in tissue density. The range andparameter settings may be configured so as to increase the accuratedetection of changes in tissue density.

The memory 130 is configured to store data it receives from the signalprocessor 120 that is either outside the normal signal range or withinthe range of signals being detected. It is fully contemplated that thememory 130 may utilize known compression algorithms and functions tosave on memory and size requirements. In this regard, it is alsocontemplated that the memory 130 may store additional data with respectto each signal such as a timestamp, the specific characteristics of thesignal, or any other relevant data. In this respect, the signalprocessor 120 and memory 130 are configured to keep the various types ofdata the orthopedic surgeon or treating physician would like to have tomonitor tissue density.

The implantable sensor 100 also includes a telemetry circuit 140. Thetelemetry circuit 140 is connected to the memory 130 and is adapted forsending the data stored in the memory outside of the patient's body toan external device 200. In particular, the telemetry circuit 140 isadapted for communicating wirelessly with the telemetry circuit 210 ofthe external device 200. There are several types of wireless telemetrycircuits that may be employed for communication between the implantablesensor 100 and the external device 200. For example, RFID, inductivetelemetry, acoustic energy, near infrared energy, “Bluetooth,” andcomputer networks are all possible means of wireless communication. Inthe present embodiment, the telemetry circuits 140, 210 are adapted forRFID communication such that the telemetry circuit 140 is a passive RFIDtag. In one aspect, the sensor is also programmed with identificationinformation concerning the type of procedure performed, the date of theprocedure and the identification of the medical devices implanted. Usinga passive RFID tag helps limit the power requirements of the telemetrycircuit 140 and, therefore, the implantable sensor 100 yet still allowswireless communication to the external device 200.

Supplying the power requirements of the implantable sensor 100 is apower source 150. In the current embodiment, the power source 150 is abattery. In this manner-the sensor may be internally powered. Thebattery power source 150 may be a lithium iodine battery similar tothose used for other medical implant devices such as pacemakers.However, the battery power source 150 may be any type of batterysuitable for implantation. The power source 150 is connected to one ormore of the transducer 110, the signal processor 120, the memory 130, orthe telemetry unit 140. The battery 150 is connected to these componentsso as to allow continuous monitoring of indicators of tissue density. Itis fully contemplated that the battery 150 may be rechargeable. It isalso contemplated that the battery 150 may be recharged by an externaldevice so as to avoid the necessity of a surgical procedure to rechargethe battery. For example, in one embodiment the battery 150 isrechargeable via inductive coupling.

In one embodiment, the sensor 100 is passive. However, it is fullycontemplated in an alternative embodiment that the sensor 100 be active.Where the sensor 100 is active, the transducer 110 uses a pulse-echoapproach to detect various aspects of tissue density, including withoutlimitation to other features, nutrient channel porosity, nutrientchannel flow, nutrient channel calcification, annulus elasticity andtissue inflammation. For example, utilization of ultrasonic waves in apulse-echo manner to determine tissue density is fully contemplated. Inthat case, the transducer 110 would utilize power from the power source150 to generate the pulse signal. In the current embodiment, however,the transducer 110 may use the power source 150 to facilitate thesending of signals to the signal processor 120. The signal processor120, in turn, may use the power source 150 to accomplish its filteringand processing and then send a signal to the memory 130. The memory 130will then use the power source 150 to store the signal and tissuedensity data.

In other embodiments the power source 150 may also be connected to thetelemetry circuit 140 to provide power to facilitate communication withthe external device 200. However, in the present embodiment thetelemetry circuit 140 does not require power from the power source 150because it communicates with the external receiver 200 utilizing apassive RFID tag type or other inductive coupling means ofcommunication. Further, the power source 150 may be connected to otherelectronic components not found in the current embodiment. It is fullycontemplated that the power source 150 may include a plurality ofbatteries or other types of power sources. Finally, it is alsocontemplated that the implantable sensor 100 may be self-powered, notrequiring a separate power supply. For example, a piezoelectrictransducer may be utilized as the acoustic transducer 110 such thatsignals detected by the transducer also provide power to the sensor 100.The piezoelectric transducer could detect the signal and converts itinto an electrical signal that is passively filtered and stored only ifit satisfies the signal thresholds. Then, as in the current embodiment,the sensor 100 may utilize a passive RFID tag or other passive telemetryunit to communicate the tissue density data with an external device.Thus, allowing the sensor 100 to function without a dedicated orcontinuously draining power source. Similarly, the sensor 100 mayutilize a piezoelectric or electromagnetic power source that is not usedas the acoustic transducer 110. For example, such power sources couldutilize patient motion to maintain a power supply.

Referring now to FIGS. 1 and 2, shown therein is an alternativeembodiment of a sensor for monitoring the spinal environment inaccordance with another aspect of the present invention. The sensorsystem is substantially similar to the other sensors described inaccordance with the present invention. However, the sensor systemincludes a transducer lead 300 for insertion into a disc space or bone(FIG. 2) and a separate main housing 350. In one aspect, the mainhousing 350 contains the remaining components of the sensor system suchas a signal processor, memory unit, telemetry unit, power supply, andany other component. As illustrated, the main housing 350 is adapted tobe positioned away from the transducer leads 300. Main housing 350 islocated outside of the exterior of the spinal column. In a furtheraspect, main housing 350 is attached to the bone 10 or positioned withinsurrounding soft tissue. Positioning the main housing 350 away from thetransducer 300 allows the transducer, which may be miniaturized, to beplaced in a desired location without requiring the additional space tohouse the remaining components of the sensor system. In one embodiment,the main housing 350 is shaped as a substantially cylindrical housing soas to facilitate implantation via a catheter.

In one aspect, transducer 300 is substantially cylindrical such that itcan be delivered to the implantation site via a needle or catheter. Inthis respect, the transducer 300 may communicate with the components inthe main housing 350 via a dedicated wire or lead 360, as shown. In afurther embodiment, the transducer 300 communicates with the componentsin the main housing 350 wirelessly. For example, the transducer 300utilizes an RF transponder or other means of wireless communication totransfer information to the main housing 350.

Though the main housing 350 is shown as being disposed inside the bodyand near the spine, in another application the main housing is disposedanywhere within communication range of the transducer 300, includingoutside the body. Thus, the main housing 350 is preferably located whereit will not interfere with the fiction of the spine nor interfere withany other body functions. Where the transducer 300 communicates with thecomponents of the main housing 350 via the wire lead 360, the locationof the main housing is limited by potential interference of both thewire and the main housing. Where the transducer 300 communicates withthe components in the main housing 350 wirelessly, the position of themain housing 350 will be a function of the limits on the distance forwireless communication as well as any potential body fictioninterference the main housing may cause. With sufficient wirelesscommunication, the main housing 350 is positioned outside the patient'sbody. Preferably, when disposed outside of the body the main housing 350will be positioned in a location anatomically close to the transducer300. Placing the main housing 350 as close to the location of thetransducer 300 as possible helps to facilitate wireless communication.It is not necessary to place the main housing 350 near the transducer300 if communication can be achieved from greater distances.

The sensors 100 and 300 may take a variety of forms, shapes and sizeswithout deviating from the present invention. For the purpose ofillustration but without limitation to alternative designs, in theillustrated embodiments the sensors are of the type to sense acousticenergy, RF energy, light energy, chemicals, PH, temperature, biologiccompounds and/or electrical conductance such as impedance. Further thesensors incorporate more than one type of sensor to permit sensing ofmultiple tissue characteristics with a single sensor or network ofassociated sensors. In a further aspect, a first tissue characteristicand a second tissue characteristic are sensed. The first and secondcharacteristics are compared, and the comparison is utilized as anindicator of tissue condition. In a still further aspect, more than twotissue characteristics are compared to generate a tissue condition.Various attributes of implantable sensors are more fully described inU.S. patent application Ser. No. 11/344,459 entitled METHODS FORDETECTING OSTEOLYTIC CONDITIONS IN THE BODY, by Nycz, et al. filed Jan.1, 2006 incorporated herein by reference in its entirety. The sensor hasa shape adapted to the planned implantation technique or location in thebody. For example, but without limitation to alternative shapes, thesensor may have the shape of a sphere, cylinder, rectangular, elongatedthin film, circular thin film, or may include a housing of one of theseshapes with leads extending to the tissue of interest shape. In oneaspect, the spherical sensor would have a diameter less than 2 cm, morepreferably less than 1 cm and still more desirable but not required, thediameter would be less than 2 mm. In a similar manner, it iscontemplated that cylindrically shaped sensors will be sized to passthrough insertion devices such as catheters and needles suitable forminimally invasive insertion. For example, the cylindrical sensor bodymay have a diameter less than 2 cm, more preferably less than 1 cm andstill more desirable but not required, the diameter would be less than 2mm. The length of the cylindrical implants may vary depending on theexpected application with typical devices ranging from 15 cm to lessthan 1 cm in length. With continued improvements in micro-scale andnano-scale technology it is contemplated that still smaller diametersensors may be used alone or in combination with a plurality of verysmall sensors sensing tissue at different locations. In one aspect, thethin film embodiments have a perimeter of a desired shape and size forthe expected application in the body or insertion technique and have athickness less than 5 mm and more desirably a thickness less than 2 mm.

The sensors 100 and 300 include processor and memory components toprocess the sensed signals and store the information for later retrievalor transmission. In one form, each sensor is formed for a particularapplication with a static program having features specific for theintended medical application. In another form, the sensor is of auniversal type with a programmable memory and processor. With theuniversal sensor embodiment, it is contemplated that the sensor will besupplied in bulk. The sensor will be programmed to operate to sense thedesired tissue characteristics of interest, report sensed signalsoutside of the established threshold values and report the informationaccording to the programmed instruction set. In one aspect, theoperational program of the universal sensor is burned-in at a productionfacility and packaged alone or with an associated implant. In thismanner, the program may not be altered by the user. In a different form,all or a portion of the operational program is installed at a productionfacility into a programmable sensor and the user may add to, change,erase and/or reprogram the sensor after delivery to the user to suittheir needs. It is contemplated that the programmable sensor is updatedby the user prior to implantation in a patient, during the implantationprocedure or at any time after implantation. In this form, all or aportion of the sensor includes an erasable programmable memory (EPROM)or flash memory. Still further, the sensor may output data by wired orwireless telemetry in any manner. Examples of various formats is providein U.S. patent application Ser. No. 11/344,667 entitled IMPLANTABLESENSOR by Donofrio, et al. filed Feb. 1, 2006 incorporated herein byreference in its entirety.

The sensors 100 and 300 of the present invention may be implanted intothe body in a variety of surgical procedures. It is contemplated thatthe approach to the patient should involved the least damage to thepatient's tissue as possible. In one aspect, implantation of the sensoris conducted via an open surgical procedure, particularly when implantedin conjunction with other load bearing implants. For example, during theexposure necessary for an interbody fusion between adjacent vertebrae V1and V2, a sensor is placed in the native bone, the fusion mass or theadjacent soft tissue. In another form, the sensor is placed incombination with a lengthening intramedullary nail such as disclosed inU.S. Pat. No. 5,704,939 incorporated herein by reference in itsentirety, having a controller adapted to be responsive to the signalfrom the sensor. Similarly, in another embodiment, a sensor may beplaced in conjunction with the implantation of motion preservingprostheses such as artificial hips, artificial knees, artificial discs,nucleus replacement, facet replacements and dynamic stabilizationdevices. However, in another aspect, it is expected that implantation ofthe sensor will be through a minimally invasive procedure adapted tominimize trauma to the patient. For example, in one embodiment a guidemember such as a needle or guidewire is positioned through the skin to aposition adjacent a spinal segment. A tubular member, such as a needleor other cannula, having an internal diameter larger than the externaldiameter of the guide member is positioned over the guide member. Theguide member is withdrawn leaving a passage to the implantation siteadjacent the spinal segment. A sensor, such as a cylindrical orspherical shaped sensor, may then be passed through the tubular memberto the implantation site. Additional features of the sensor, theimplantation instruments and surgical techniques are disclosed in U.S.patent application Ser. No. 11/344,999 entitled IMPLANTABLE PEDOMETER byDonofrio et al. filed Feb. 1, 2006 incorporated herein by reference inits entirety.

In one aspect, the sensor will be placed in tissue that will havesufficient tissue strength to maintain its position in the body. Forexample, in one embodiment the sensor includes an exterior surfacefeature for engaging the bone of a vertebral body. In still a furtherembodiment the external surface is roughened or bristled to engage thesoft tissue adjacent to the a spinal segment. In still a furtherembodiment, the sensor is placed subcutaneously spaced from the spinalcolumn with sensing means to sense tissue characteristics of the spinalcolumn. In other implantation procedures, the sensor unit 100 ispress-fit into an opening formed in a bone. It is contemplated thatafter the sensor unit 100 has been press-fit into the prepared openingthat it may then be sealed into the bone. The sensor unit 100 may besealed into the bone using a variety of techniques. These sealingtechniques may include, but are not limited to, fibrin glue, PMMA,collagen, hydroxyappetite, bi-phasic calcium, resorbable polymers orother materials suitable for implantation. Additionally oralternatively, in another embodiment the sensor unit 100 is sealed intothe bone by a later implanted implant, or any combination of thesetechniques. For example, the sensor unit 100 is sealed in by any of theabove mentioned materials in combination with an additional implant toprovide enhanced fixation. In this manner, the sensor unit 100 isimplanted either prior to the implantation of an implant or as a standalone unit—where no implant is to follow.

Still further, in an alternative embodiment the sensor includes sensors300, lead 360, and a main body 350 such as the sensor shown in FIGS. 1and 2. In one aspect, the sensors 300 are implanted at least partiallywithin the disc space to sense the intradiscal environment. In analternative embodiment, the sensors 300 are positioned in contact withor adjacent to the annulus between adjacent vertebral to sense signalsindicative of the annulus or disc environment. In still a furtherembodiment, the sensors 300 are placed approximate the exiting nerveroots to detect signals indicative of nerve condition and health. Thesensors are placed in any position suitable to detect the environmentalcondition of the spinal segment. In each of these positions, the mainbody 350 of the sensor is positioned away from the sensors to limitinterference with normal patient function and movement or to provideeasier communication and powering by external devices. While it iscontemplated that the main body 350 will be implanted, in one embodimentthe main body 350 is positioned outside the patient with wired orwireless communication occurring between the sensing leads and the mainbody.

As shown in FIGS. 1-4, the external device 200 receives the tissuedensity data from the implantable sensor 100 or main housing 350 viacommunication between the telemetry circuit 140 of the sensor and thetelemetry unit 210 of the external device. Then a signal processor 220converts or demodulates the data. The converted data is output to adisplay 230 where it is displayed in human intelligible form. Theconversion and processing of the data may be tailored to the specificliking of the health care provider. For example, the display of data maysimply be a number representing the number of signals recorded by thememory 130 indicating the number of signals outside the normal rangethat were detected. Similarly, the display of data may be a bar graphhaving a height or length representing the number of signals detected.Further, the display may show a detailed chart of specific informationfor each signal detected outside of the threshold range. These variousdisplay examples are for illustration purposes only and in no way limitthe plurality of ways in which the tissue density data may be displayedin accordance with the present invention.

FIG. 4 illustrates one embodiment of a flow chart for tissue densitydata detection, processing, and output employing the current embodimentof the invention. The internal monitoring process occurring within thesensor 100 constitutes a continuous loop of monitoring and storing thetissue density data. In step 410, the acoustic transducer 110 listensfor signals indicative of tissue density. Upon detecting a signal thesignal processor 120 determines in step 420 if the signal meets thepreset parameters. If the signal does not meet the thresholds, then thesignal processor 120 does nothing and returns to listening 410. If thesignal does meet the parameters, then the signal processor 120 passesalong a signal to the memory 130. The memory 130 stores the tissuedensity data accordingly at step 430. The internal process returns tostep 410 as the acoustic transducer 110 listens for the next tissuedensity signal.

Also within the sensor 100, a communication process is underway. In step440, the telemetry unit 140 awaits communication from the externaldevice 200 requesting transmission of the tissue density data. If thetelemetry unit 140 receives such a request, then at step 450 thetelemetry unit 140 transmits the tissue density data to the telemetryunit 210 of the external receiver 200. At step 460, the receiverreceives the data and the signal processor 220 converts or demodulatesthe transferred data at step 470. The display 230 displays thedemodulated data in a human intelligible form at step 480. At this pointthe surgeon or other health care provider can review the tissue densitydata and take the appropriate medical action as they see fit.

Though not illustrated, it is also contemplated that one embodiment theexternal device 200 resets the tissue density data stored within thesensor 100. For example, the external receiver 200 is configured toreset or clear the memory 130 upon extraction of the tissue densitydata. The external device 200 may clear the memory 130 of the sensor 100by utilizing communication between the telemetry circuits 140, 210.However, it is not necessary for the external device 200 to clear thedata of the sensor 100. For example, a treating physician may wish tokeep a running count of signals detected outside the normal range in thememory 130 rather than resetting the sensor 100 after each dataextraction.

Described below are numerous components of the external receiver inaccordance with the present invention. These components illustrate thevarious types of electronic and non-electronic components that may beutilized by the external receiver. These descriptions are exemplary ofthe type of components that may be employed by the external receiver,but in no way are these illustrations intended to limit the types orcombinations of electronic and non-electronic components that may beutilized in accordance with the present invention.

The external receiver may include components such as a telemetry unit, asignal processor, a calibration unit, memory, an indicator, and anetworking interface. The telemetry unit is adapted for communicationwith the implantable sensor in accordance with the present invention.Thus, the telemetry unit is configured to extract tissue density datafrom the sensor. The telemetry unit may obtain data from the sensorthrough a variety of wireless communication methods such as inductivecoupling, capacitive coupling, radio frequency, personal computernetworking, Bluetooth, or other wireless means. Though the preferredmethod of communication is wireless, it is also contemplated that theexternal receiver may be in selective wired communication with theimplantable sensor.

Once the data is obtained by the external receiver using the telemetryunit, the data is processed by the signal processor. The degree and typeof data processing is dependent on both the data obtained from theimplantable sensor and the desires of the treating doctor. The dataprocessing performed by the signal processor may range from simpleconversion of tissue density data into a human sensible form to complexanalysis of the usage data via spectral analysis. Further, the dataprocessing performed by the signal processor may only be a first step ofprocessing. The processed data of the external receiver may be output toa more powerful or specialized signal processing unit where additionalprocessing takes place. This additional signal processing unit may belocated either within the external receiver itself or in a separateexternal device such as a personal computer.

The signal processor is adapted for converting the data into a form thatmay be utilized by an indicator. The indicator may be any type of deviceor interface that can output the data in human intelligible form. Forexample, the indicator may be a visual display, speaker, or any otherindicator or output means. It is contemplated that the indicator may becomposed of a plurality of output mechanisms instead of a single device.

The external receiver includes a calibration circuit in one embodiment.The calibration circuit is adapted for configuring a configurable signalprocessor of an implantable sensor. The external receiver may set,restore, or change such aspects of the configurable signal processor asthe predetermined criteria for keeping sound recordings, the type oftissue density data to be kept, the preset thresholds for signalsindicative of normal tissue density, or any other setting related to theperformance of the configurable signal processor. It is fullycontemplated the calibration circuit may utilize the telemetry circuitsof the sensor and external receiver to communicate with the configurablesignal processing unit. However, it is also fully contemplated that thecalibration circuit and the configurable signal processing unit may havea separate dedicated means of communication.

In one embodiment, the external receiver includes a memory unit. Thememory unit may be adapted for multiple uses. First, the memory unit maybe adapted for permanent storage of tissue density data obtained fromthe implantable sensor. Thus, the memory unit may store data obtained atvarious times from the implantable sensor so the data may later bereviewed, compared, or analyzed. Second, the memory unit may be adaptedfor temporary storage of tissue density data obtained from theimplantable sensor. In this case, the memory unit will store the datauntil it is either discarded or transferred for permanent storage. Forexample, the data may be transferred from the memory unit of theexternal receiver via a networking interface to a network or computerfor permanent storage.

When present, the networking interface provides a means for the externalreceiver to communicate with other external devices. The type of networkutilized may include such communication means as telephone networks,computer networks, or any other means of communicating dataelectronically. The networking interface of the external receiver couldobviate the need for the patient to even go into the doctor's office forobtaining implant usage data. For example, the patient could utilize theexternal receiver to obtain the usage data from the implantable sensoron a scheduled basis (e.g. daily, weekly, monthly, etc.). Then,utilizing the networking interface the patient could send this data tothe treating doctor. In one aspect, the networking interface isconfigured to directly access a communication network such as atelephone or computer network for transferring the data. It is fullycontemplated that the computer network be accessible by a treatingphysician for reviewing implant usage data of the patient withoutrequiring the patient to make an actual visit to the doctor's office.The networking interface may be similar to the CareLink system fromMedtronic, Inc.

Further, it is also contemplated that any communication between theexternal receiver and the computer network may be encrypted or otherwisesecured so as protect the patient's privacy. It is also contemplatedthat the networking interface may be configured for communication with aseparate device that is adapted for accessing the communication network.For example, the networking interface may be a USB connection. In oneembodiment, the external receiver is connected to a personal computervia the USB connection and the personal computer is be utilized toconnect to the communication network, such as the internet, fortransferring the data to a designated place where the treating doctormay receive it.

The disclosed sensors for detecting indicators of changes in the spinalsegment environment are utilized in numerous applications. For example,but without limitation to other uses, in one embodiment the detectedchanges are used to predict the onset of herniation of the disc, discbulges, annulus tears, degeneration of the disc nucleus, inflammation,pain localization, myelin sheath changes, presence of abnormal chemicalor biologic agents, therapeutic agent concentrations, spatialrelationship of spinal components, pressure, tension, relative motionbetween spinal components, bone growth, nutrient channel fiction, facetfunction, adhesion growth and location, instantaneous axis of rotation,implant usage, implant degradation, and presence and amount ofparticles. Further, in another aspect the sensors are placed at a firstspinal level to provide data on the localized conditions and similarsensors are placed at other spinal levels to provide similar sensed datafor comparative analysis for diagnosis and treatment.

In one aspect, sensors of the present invention may be used in diagnosisof patients presenting with spinal pain or degeneration. At times, it isdifficult for the healthcare provider to identify with certainty theprecise cause of the back pain being experienced by the patient. Evenafter imaging the spine, the area causing the pain may not be readilyidentifiable. In this aspect, one or more sensors in accordance with thepresent invention is placed adjacent one or more spinal segments priorto provide sensed data to the health care provider. For example, butwithout limitation, in the case of radiculitis where the pain isdiffuse, the sensors are programmed to seek characteristics of inflamednerves adjacent each spinal segment. For example, sensors at multiplelevels may gather data on the size and geometry of the exiting nerveroots. Based on comparative analysis, the surgeon may be able to moreaccurately determine the nerve root causing the pain. Further, in anadditional embodiment the sensors also include chemical or biologicsensors to detect the presence of inflammatory agents adjacent thenerves. This would be an indicator of nerve distress and potentialpatient pain. Still further, in one embodiment a sensor is configured todetect electromyography (EMG) signals associated with musclestimulation. Other useful sensors that are used alone or in combinationwith the foregoing sensors include temperature or PH to detect changesin the body indicative of a localized response to pain transmission.With this information, the care giver may determine the course ofnon-invasive treatment or surgical options. For example, in one method afirst treatment course of a first pharmaceutical compound or compoundsat a first dosage is prescribed for a first period. The sensors evaluatethe indicators of nerve inflammation and provide the sensed data to thecare giver. Based on the sensed data, the treatment continues if thereis sensed a positive change in the patient. However, if the sensorsdetect little change or a worsening condition, the first pharmaceuticalcompound or compounds is changed to a second treatment course of asecond dosage, or alternatively a second pharmaceutical compound orcompound is prescribed at a third dosage. The process of treating withpharmaceuticals and sensing changes in the patient continuesindefinitely as desired by the caregiver and patient. As explainedfurther below, in another aspect this process is automated by having thesensor data transmitted to an indwelling supply of a treatment agentthat can be released as sensed data crosses the programmed thresholds.Moreover, in one aspect the sensor notifies the patient of conditionsneeding urgent attention as soon as possible and of degeneratingconditions needing attention in a matter of days, weeks or months.

In another application, sensors according to the present invention arepositioned to monitor the intradiscal space. For example, the nutrientsystem supplying the nucleus may be evaluated to determine whethernon-invasive or minimally invasive treatments may be effective for thepatient. In one aspect, the sensor is configured to evaluate theopenings in the endplates of the vertebrae adjacent the disc space.These openings allow nutrients to flow into the disc space and nourishthe disc nucleus. In one aspect, the sensors are be programmed to detectthe size, spacing and distribution of the nutrient openings to providean assessment of the expected flow of nutrients. Further oralternatively, in another aspect the sensors detect the presence andconcentration of one or more nutrients to evaluate the health of thenutrient flow. If the health of the nutrient flow system is sufficient,the health care provider may prescribe a first treatment course ofpatient rest, external mechanical unloading of the segment or minimallyinvasive internal mechanical unloading of the segment. In theseconditions the nucleus may heal to substantially its normal condition.In one treatment method, as part of the first treatment course the careprovider also prescribes a treatment compound to increase the nutrientsreaching the nucleus. For example, but not as an exclusive listing,pharamceutical agents such as pain killers, steroids, anti-inflammatorydrugs, growth hormones or factors may be taken orally, injected,delivered intravenously, delivered transdermally, metered with a pump orplaced on a microchip assay. Either indwelling or instrument placedsensors are used to monitor the tissues adjacent the spinal segmentbeing treated. If the sensed changes are above a first threshold valueindicating a worsening condition, the patient is switched to a secondcourse of treatment compounds and/or surgical intervention. In thealternative, the sensed data may indicate that conservative care isunwarranted and urgent surgery to remove all or a portion of thenucleus, or an operation to open existing nutrient channels in theendplates or create new nutrient channels in the endplates is the bestcourse of care. Thus, the sensor system according to the presentinvention detects the disc nucleus system health and provides data toselect between non-invasive, minimally invasive and invasive proceduresto treat the sensed disc space condition.

In still a further treatment option, sensors according to the presentinvention are left in a patient indefinitely to provide periodicinformation on the skeletal system conditions. Comparative analysis ofthe periodic readings provides the care giver with a picture of thecurrent health of the skeletal system and the ongoing patient healthtrend. With this information, the care giver advises the patient of theappropriate treatment option along the continuum of care available tohealth care providers treating a patient suffering from back or otherskeletal problems. For example, but without limitations to alternativetreatments, in one aspect the care provider advises the patient in afirst treatment course to make life style changes; including diet,nutritional supplements, rest and exercise. Based on sensed data, asecond treatment course is initiated that includes, for example, atreatment compound regime; increase or alter a current pharmaceuticalregime; seek non-invasive intervention including external mechanicalunloading, therapeutic agent pumps, transdermal delivery devices; seekminimally invasive intervention often without joint capsule invasion; orseek invasive treatments to the spinal segment often with joint capsuleinvasion. Examples of minimally invasive intervention include bone burrremoval, rotator cuff repair, cartilage repair, facet spacers, spinousprocess spacers, spinal tethering, and dynamic stabilization. Examplesof invasive intervention include nucleus replacement, interbody fusion,artificial disc placement, artificial knee placement, artificial hipplacement, spinal posterior fixation, spinal anterior fixation andspinal lateral fixation. Each of the above can be considered a firsttreatment course with each successive treatment, including cessation ofthe first treatment, being the second treatment course, the thirdtreatment course, etc. until patient relief is obtained.

The sensors of the present invention are designed to be usedintraoperatively. For example, sensors are placed on or near the annulusof the affected spinal segment disc space and/or the facet jointconnective fibers defining the facet joint annulus. The sensor orsensors detect the condition of the annulus during disc spacedistraction and interbody spacer placement. In one embodiment, thesensor provides the surgeon with an indication of whether the properannulus tension has been reached and a warning when the annulus tensionexceeds the desired amount such that permanent damage is imminent withfurther distraction. In one aspect, an additional sensor is placed on ornear an adjacent spinal level annulus. In this aspect, the tension inthe affected spinal segment annulus is compared to the adjacent levelannulus, such that the surgeon may tension the affected level annulus toapproximate the tension sensed in the adjacent spinal level annulus. Inone aspect, evaluation of the annulus includes sensing thecharacteristics of sharpie fibers within the annulus walls. The sharpiefibers are a part of the annulus adhered to the bone and may experiencethinning or bulging in degenerative conditions and during excessiveintraoperative distractions.

A still further use of spinal segment sensors according to the presentinvention is to determine the instantaneous axis of rotation (LAR) ofone or more spinal segments. In this application, the sensor isconfigured and programmed to sense the IAR of a spinal segment andtransmit the sensed data to a health care provider. Either manually orvia computer, the data is used to determine the ideal position for thelocation of an implant within the disc space. The placement of animplant to maintain or restore the natural IAR can be important toprevent the IAR of adjacent spinal levels from changing as a result ofthe implant placement or the improperly placed implant may wear morequickly or dislodge as a result of being of center from the natural IAR.

In another aspect of the present invention, sensors remain in place orare positioned during a surgical operation on an affected skeletalportion. The sensor(s) provides data to the care giver concerning thehealing of the affected skeletal portion. For example, the sensor isprogrammed to detect the presence and location of adhesions adjacent thesurgical site. This may assist the care giver in rehabilitationtreatment and/or the need for surgical release of the adhesions.Further, the sensors monitor the patient and implant range of motionearly in the recovery process to ensure the best possible outcome.Experience has shown that waiting too long after surgery to recover thefull range of motion may inhibit the patient from ever obtaining thefull range of motion of a joint or complete healing of bone. Examples ofsurgical procedures include placement of artificial discs in the spine,anterior cruciate ligament reconstruction in the knee, limb lengthening,artificial hips, and artificial knees. Moreover, in an additional aspectthe sensor monitors patient compliance with rehabilitation programs suchas stretching, exercise and rest. Historical range of motion data fromthe sensors can also be used to evaluate the ability of the patient towork in a given occupation and/or qualify for workers compensationbenefits. Still further, the sensed information detects patient behaviordetrimental to the healing process such as too much strenuous activitytoo early after surgery. These conditions can be addressed with thepatient by the care giver. For example, a first course of rehabilitationcare may be initiated following an initial treatment. Based on senseddata indicating the healing and/or health of the skeletal segment, asecond course of rehabilitation care may be initiated. If the sensorsare left in place indefinitely, they can be periodically accessed toprovide historic data on implant usage, particle debris presence andconcentrations such as silicone or carbon fiber particles.

In yet another aspect, a sensor according to the present invention ispositioned to monitor the intradiscal space to evaluate healing andgeneral health characteristics. For example, in this application thesensor periodically checks the endplate nutritional channels to evaluatesize and distribution to assess potential calcification in progress.Further, the sensor detects the flow, presence, and/or concentration ofnutrients in the fluid of intradiscal space to provide an approximationof the disc space health. The sensor may also detect the properties ofthe nucleus, such as height, density, water content, and mineral contentto evaluate the health of the nucleus. In still a further embodiment,either in combination with the other sensor features or separately, asensor monitors the intradiscal space for temperature, PH and thepresence of inflammatory response agents such as cytokines. The sensor,or an external device, records readings over a period of time toindicate to the patient or care giver the presence of conditions needingimmediate medical attention or degenerative conditions needing attentionat some point in the next few days, weeks or months.

Referring now to FIGS. 5 and 6, there is shown instrumentation for usein or in conjunction with surgical procedures. Each figure shows aportion of the vertebral column with vertebral bodies V1, V2 and V3separated by intervening disc spaces. In FIG. 5, a sensing instrument500 is shown. Instrument 500 has a main body 502, a proximal end 504,and a distal end 506. The main body 102 includes a gripping surface 508for grasping by the user or engagement with a further instrument. Theproximal end 504 is adapted for placement adjacent the annulus surface520 of the disc space being assessed when the electronic instrumentation500 is in use. Thus, the distal end 506 is disposed distally to thetissue being assessed when the electronic instrumentation 500 is in use.The electronic instrumentation 500 of FIG. 5 also includes a display 508and a fiducial marker assembly 510. The fiducial marker assembly 510 isjoined to distal end 106. A longitudinal axis extends along at least aportion of the main body 502.

The main body 502 is adapted for housing the various electroniccomponents of the electronic instrumentation 500. In FIG. 5, the mainbody 502 is shown as being substantially cylindrical and elongated. Thisis merely for illustrative purposes. It is fully contemplated that themain body 502 may take any shape capable of holding the components ofthe electronic instrumentation 500, including non-cylindrical andnon-elongated designs. However, it is preferred that the main body 502be of appropriate shape and size to be portable and handheld. Forexample, but without limitation, in further embodiments the main body isshaped similar to an injector gun, laser pointer, or pen. Still further,in another embodiment the main body 502 is narrow like a catheter orneedle and is manipulated remotely for minimally invasive surgery.

The tip 504 is shown extending through annulus 520 between superiorvertebral body V2 and inferior vertebral body V3. The sensor associatedwith instrument 500 includes the same sensing capabilities discussedabove with respect to the implantable sensors 100 and 300 and may beused in the same manner on a handheld or percutaneous basis. Oncepositioned in the disc space, the sensor evaluates the vertebralendplates 522 and 524. For example, it determines the total volume ofthe space between the endplates and annulus to thereby calculate theproper sizing of a spacing implant to be inserted into the disc spaceand/or the amount of filling material to be inserted into the disc spaceto promote fusion between V1 and V2. Further, as described more fullyabove, the sensor instrument 500 is used to evaluate the nutrientchannels extending through endplates 522 and 524. In a further aspect,the sensor detects the extent of herniation or bulging of the posteriorportion 526 of the annulus. It is often necessary to decrease oreliminate this bulging during the operation to provide the patient withthe appropriate pain relief. In still a further use, the instrument isused to sense the three dimensional shape of the endplates and providethe user with this information. In one aspect, a processor evaluates thesensor signals and determines the appropriate geometric relationshipsbased on the sensed data. An appropriate sized nucleus or other spacermay be selected based on the sensed endplate geometry. As a further aidto implant placement, in another aspect the sensor is used to detect theLAR for one or more disc spaces. The information from the handheldsensor is conveyed wirelessly, through a wired connection or throughconnection to a computer system through a data port such as a USB port.Similar devices are disclosed in United States Patent Applicationentitled SURGICAL INSTRUMENT TO ASSESS TISSUE CHARACTERISTICS, by Nyczet al. filed on even date as attorney docket No. P22320.00/31132.426which is incorporated herein by reference in its entirety.

Referring now to FIG. 6, there is shown a series of sensors 610, 620,and 630 placed adjacent the disc space between four adjacent vertebralbodies. Although sensors 610, 620 and 630 are shown as large rectangularshapes for the purpose of illustration, in one embodiment the sensorleads are less than 3 mm in width and approximately the same dimensionin length. In one approach, the sensors 610, 620, and 630 are placedthrough a minimally invasive procedure, such as percutaneous placementvia guided catheter or needle, in contact with or closely adjacent tothe annulus tissues of the spinal segment. The sensors are joined to therespectively main housings 614, 624, and 634 by connectors 612, 622 and623, respectively. Connectors 612, 622, and 632 may include multiplesensors along their length. Further, main housing 624 may be used alonewith sensors 610, 620 and 630 being directly connected to the mainhousing via connectors or wirelessly. In this manner, sensor signals aretransmitted to the main housings positioned outside of the patient.Additionally, in one approach the connectors are used to extract thesensor leads after completion of the operation. In one aspect, sensors610, 620 and 630 of the sensor provide information on the annulustension. As explained above, if the disc space between V2 and V3 is theaffected disc space being operated upon, the sensor will provide thesurgeon with a “go” for further tension on the annulus as compared tothe adjacent annulus or a “stop” when the appropriate tension has beenreached matching or approximating the tension of the adjacent spinallevels. In another aspect, the sensor are positioned closer to theexiting nerve roots and provided data on the condition of the nerveroots and the location of potential sources of pain for the patient.Still further, in one diagnostic procedure, the sensors are left inposition as the patient is moved through a series of predeterminedmotions. The sensors detect the IAR for each level and provide this datato the health care provider. The sensed IAR is then used by the surgeonto assist in proper placement of an interbody implant, such as a nucleusor artificial disc replacement device. During the operation, the sensorremains in place and indicates to the surgeon when the implant is in thesensed LAR position and provides a signal to maintain the position ofthe implant in the current position.

In addition to sensing the intradiscal environment prior to implantinsertion, the instrument 500 is used after implant or graftpositioning. In this embodiment, the instrument probes the disc spaceand indicates to the user the presence of any inappropriate materials.For instance, in a nucleus replacement or treatment procedure, boneparticles from the endplates should not be present in the disc space.Alternatively, for fusion procedures the presence of nucleus material inor adjacent the graft material is contraindicated. Finally, in oneaspect the instrument is inserted into the surgical wound. Theinstrument is energized and provides the user with an indication of anyforeign materials remaining at the surgical site. For example, in thisembodiment the instrument is programmed to detect surgical instrumentsremaining in the patient.

Referring now to FIGS. 7-10, there is described use of sensors accordingto one aspect of the present invention in combination with controllabletreatment devices. FIG. 7 illustrates a dynamic fixation system 990extending between vertebrae V1, V2 and V3. Dynamic fixation system 990includes a first bone fixation screw 1012 inserted into the pedicle ofvertebra V1, a second bone fixation screw 1016 inserted into the pedicleof vertebra V2 and a third bone fixation screw 1022 inserted into thepedicle of vertebra V3. Each screw 1012, 1016 and 1020 are attached to arod segment 1014, 1018 and 1020, respectively. A first dynamic actuator1000 interconnects rod segments 1014 and 1018, and a second dynamicactuator 1010 interconnects rod segments 1018 and 1020. As shown in FIG.8, dynamic actuators each included a receiver 1002 to receive data orcontrol signals and a processor 1004 with associated memory 1006 tooperate the actuator 1008. The dynamic actuators are operable to controlthe tension and/or compression on the adjacent rods. In a further aspectof one embodiment, dynamic actuators dampen movement between the rodsand are controllable to stiffen or loosen the dampen force applied onthe rods. In the illustrated embodiment, a sensor 900 is positioned inthe space between vertebrae V1 and V2, and a similar sensor 910 ispositioned in the space between vertebrae V2 and V3. In one aspect, thesensors sense pressure between the adjacent vertebrae and send a firstsignal indicating when pressure is above a first preset threshold levelor send a second signal when pressure is below a second preset thresholdlevel. As explained above, the threshold levels may be adjusted by selflearning of the sensor or by external communications. If a first signalis sent by sensor 900, actuator 1000 will be controlled to increasecompression on rods 1014 and 1018 to remove some of the load from thespace between vertebrae V1 and V2. If a second signal is sent by sensor900, then actuator 1000 decreases compression on the rods 1014 and 1018such that more force is experienced across the disc space betweenvertebrae V1 and V2. It will be understood that in a fusion procedurebone has a tendency to grow in the presence of moderate compressiveforces and atrophy in the absence of adequate pressure. In a fusionembodiment, sensor 910 and actuator 1010 operate to maintain thepressure across the disc space in the therapeutic range to promote bonegrowth. While a dynamic rod system has been shown for the purpose ofillustration, it is contemplated that other types of dynamic loadbearing systems will benefit from the disclosed combination, includingbut not limited to nucleus replacement devices, artificial discs,interbody spacers, anterior and posterior plating system, tetheringsystems, spinous process spacers, or facet spacers.

In another form of the invention a sensor 900 is positioned inassociation with a dynamic mechanical implant having a controllerresponsive to a sensor signal from the sensor. The controller controlsthe mechanical implant between treatment modes. In one form, themechanical implant is configured for placement on the skeletal system toassist in obtaining union or fusion of two bone segments. The sensorsenses pressure across the fracture or senses indicators of bone growthand provides a responsive signal to the controller. In one aspect, thedynamic mechanical implant is controlled-in response to one or moresignals from the sensor to maintain optimum compression across the bonefracture to promote bone growth. In another embodiment, the mechanicalimplant includes an electrical stimulation circuit adapted to energizethe bone, either with current or generation of a magnetic field, topromote bone growth. The sensor monitors bone growth across the fracturebetween two bone segments or the bone growth on the surface of theimplant and provides a corresponding sensor signal. The controllerreceives the sensor signal and controls the electrical stimulationcircuit to change from a first treatment mode to a second treatmentmode. An example of such a stimulation system is provided in U.S. patentapplication Ser. No. 11/344,668 entitled IMPLANTABLE TISSUE GROWTHSTIMULATOR, by Nycz, filed Feb. 1, 2006.

In still a further embodiment, a sensor 900 is positioned in associationwith a limb lengthening device, such as an intramedullary nail. Thesensor monitors the growth of bone and/or soft tissue across thefracture line between adjacent bone segments. The sensor provides asignal corresponding to the sensed bone formation characteristic, suchas calcification, or soft tissue tension to the limb lengthening device.A controller on the limb lengthening device then actuates the limblengthening device to advance from a first length to a second length toinhibit complete fusion between the bone segments and continue thelengthening process. In a further embodiment, the lengthening deviceincludes bone growth promoting substances or stimulators which may alsobe activated in response to sensed tissue characteristics.

Referring now to FIG. 9, there is shown a dynamic treatment systemaccording to another aspect of the present invention. In a firstembodiment, a sensor 1050 is disposed in the intradiscal space betweenvertebrae V2 and V3. Sensor 1050 includes the same features andcapabilities as sensors 100 and 300 described above. Sensor 1050 is incommunication with a therapeutic treatment reservoir 1052 disposedwithin vertebra V2. Sensor 1050 is programmed to sense the intradiscalenvironment as previously described above. In response to degradation ofthe disc space nutrients or physical structure of the spinal segment,sensor 1050 transmits a signal to the reservoir 1052. Based on thesignal received, reservoir 1052 will release one or more treatmentcompounds to addressed the sensed deficiency in the disc space. Asdisclosed in U.S. Pat. No. 6,849,463 assigned to Microchips,incorporated herein by reference in its entirety, reservoir 1052 mayinclude an array of selectively openable reservoirs and a processor fordetermine which reservoir should be opened. In a further aspect, thesensor and reservoirs are integrated into a single treatment unit 1060shown disposed in the disc space between vertebrae V1 and V2. In thisembodiment, the sensor is directly wired to the reservoir processor.Further, it is contemplated that one or more reservoirs may provide thetreatment compound to the area outside the spinal segment. Alternativelyor in addition to exterior treatment compounds, in one embodiment thereservoir is placed within the bone and the treatment compounds arediffused into the disc space through the nutrient channels or fed intothe vertebral body adjacent the endplates such that they may enter thedisc space through the natural nutrient channels, or man made channels,in the endplates to supply the treatment compound into the disc space.In another aspect, the sensor and reservoir are associated with otherstructures of the spinal segment such as the facets, annulus, nerveroots and spinal canal.

Examples of treatment compounds suitable for use with the presentinvention include but are not limited to a “biologically activecomponent”, with or without a “biological additive”. A “biologicallyactive component” includes but is not limited to anti-cytokines;cytokines; anti-interleukin-1 components (anti-IL-1); anti-TNF alpha;“growth factors”; LIM mineralization proteins; “stem cell material”,autogenic chondrocytes; allogenic chondrocytes, such as those describedin U.S. Patent Application Publication No. 2005/0196387, the entiredisclosure of which is incorporated herein by reference; autogenicchondrocytes with retroviral viral vector or plasmid viral vector;allogenic chondrocytes with retroviral viral vector or plasmid viralvector; and fibroblasts. The acronym “LIM” is derived from the threegenes in which the LIM domain was first described. The LIM domain is acysteine-rich motif defined by 50-60 amino acids with the consensussequence CX₂CX₁₆₋₂₃HX₂CX₂CX₂CX₁₆₋₂₁CX₂(C/H/D), which contains twoclosely associated zinc-binding modules. LIM mineralization proteinsinclude but are not limited to those described in U.S. PatentApplication Publication No. 2003/0180266 A1, the disclosure of which isincorporated herein by reference. “Growth factors” include but are notlimited to transforming growth factor (TGF)-beta 1, TGF-beta 2, TGF-beta3, bone morphogenetic protein (BMP)-2, BMP-3, BMP-4, BMP-6, BMP-7,BMP-9, fibroblast growth factor (FGF), platelet derived growth factor(PDGF), insulin-like growth factor (ILGF); human endothelial cell growthfactor (ECGF); epidermal growth factor (EGF); nerve growth factor (NGF);and vascular endothelial growth factor (VEGF). “Anti-IL-1” componentsinclude but are not limited to those described in U.S. PatentApplication Publication Nos. 2003/0220283 and 2005/0260159, the entiredisclosures of which are incorporated herein by reference. “Stem cellmaterial” includes but is not limited to dedifferentiated stem cells,undifferentiated stem cells, and mesenchymal stem cells. “Stem cellmaterial” also includes but is not limited to stem cells extracted frommarrow, which may include lipo-derived stem cell material, andadipose-derived stem cell material, such as described in U.S.Publication Nos. 2004/0193274 and 2005/0118228, each of which isincorporated herein by reference. “Stem cell material” also includes butis not limited to stem cells derived from adipose tissue as described inU.S. Patent Application Publication Nos. 2003/0161816, 2004/0097867 and2004/0106196, each of which is incorporated herein by reference.

A “biologically active component” also includes but is not limited tocartilage derived morphogenetic protein (CDMP); cartilage inducingfactor (CIP); proteoglycans; hormones; and matrix metalloproteinases(MMP) inhibitors, which act to inhibit the activity of MMPs, to preventthe MMPs from degrading the extracellular matrix (ECM) produced by cellswithin the nucleus pulposus of the disc. Exemplary MMP inhibitorsinclude but are not limited to tissue inhibitors, such as TIMP-1 andTIMP-2. Certain MMP inhibitors are also described in U.S. PatentApplication Publication No. 2004/0228853, the entire disclosure of whichis incorporated herein by reference.

A “biologically active component” also includes but is not limited toallogenic or xenogenic disc annulus material, such as described in U.S.Patent Application Publication No. 2005/0043801, the entire disclosureof which is incorporated herein by reference; biologic tissues, such asthose described in U.S. Patent Application Publication No. 2003/0004574,the entire disclosure of which is incorporated herein by reference; anactivated tissue graft, such as described in U.S. Patent ApplicationPublication No. 2005/0136042, the entire disclosure of which isincorporated herein by reference; an engineered cell comprising anucleic acid for encoding a protein or variant thereof, such as a BMP, aLIM mineralization protein, or an SMAD protein as described in U.S.Patent Application Publication Nos. 2003/0219423 and 2003/0228292, theentire disclosures of which are incorporated herein by reference; and arecombinant human bone morphogenetic protein, such as described in U.S.Patent Application Publication No. 2004/0024081, the entire disclosureof which is incorporated herein by reference.

As used herein, a “biological additive” includes but is not limited to“biomaterial carriers”, “therapeutic agents”, “liquids” and“lubricants.”

“Biomaterial carriers” include but are not limited to collagen, gelatin,hyaluronic acid, fibrin, albumin, keratin, silk, elastin,glycosaminoglycans (GAGs), polyethylene glycol (PEG), polyethylene oxide(PEO), polyvinyl alcohol (PVA) hydrogel, polyvinyl pyrrolidone (PVP),co-polymers of PVA and PVP, other polysaccharides, platelet gel,peptides, carboxymethyl cellulose, and other modified starches andcelluloses. Collagen includes but is not limited to collagen-basedmaterial, which may be autogenic, allogenic, xenogenic or ofhuman-recombinant origin, such as the collagen-based material describedin U.S. Patent Application Publication Nos. 2004/0054414 and2004/0228901, the entire disclosures of which are incorporated herein byreference.

“Therapeutic agents” include but are not limited to nutrients,analgesics, antibiotics, anti-inflammatories, steroids, antiviricides,vitamins, amino acids and peptides. Nutrients include but are notlimited to substances that promote disc cell survival, such as glucoseand pH buffers, wherein the pH buffer provides a basic environment inthe disc space, which preferably will be a pH of about 7.4. Analgesicsinclude but are not limited to hydrophilic opoids, such as codeine,prodrugs, morphine, hydromorphone, propoxyphene, hydrocodone, oxycodone,meperidine and methadone, and lipophilic opoids, such as fentanyl.Antibiotics include but are not limited to erythromycin, bacitracin,neomycin, penicillin, polymyxin B, tetracyclines, viomycin,chloromycetin and streptomycins, cefazolin, ampicillin, azactam,tobramycin, clindamycin and gentamycin.

“Liquids” include but are not limited to water, saline andradio-contrast media. Radio-contrast media includes but is not limitedto barium sulfate, or a radio contrast dye, such as sodium diatrizoate(HYPAQUE™).

“Lubricants” include but are not limited to hyaluronic acid, a salt ofhyaluronic acid, sodium hyaluronate, glucosaminoglycan, dermatansulfate, heparin sulfate, chondroitin sulfate, keratin sulfate, synovialfluid, a component of synovial fluid, vitronectin and rooster combhyaluronate.

A biological treatment may be introduced to an area of the skeletalsystem, such as a motion segment, by any method and in any formappropriate for such introduction. For example, the biological treatmentcan provided in a form that can be injected, deposited, or applied, as asolution, a suspension, emulsion, paste, a particulate material, afibrous material, a plug, a solid, porous, woven or non-woven material,or in a dehydrated or rehydrated state. Suitable forms for a biologicaltreatment include those described in U.S. Patent Application PublicationNos. 2005/0267577, 2005/0031666, 2004/0054414, and 2004/0228901, each ofwhich is incorporated herein by reference.

In operation, the sensors and dynamic systems of FIGS. 7-10 operate asdescribed in FIG. 10. In step 1110, the sensor monitors indicators ofthe spinal segment health. If the sensed indicator is not above thethreshold, the sensor continues to monitor. If the sensed indicator isabove a programmed threshold, in step 1120 the process continues ontothe communication process in step 1140. If the sensor is unable totransmit the data, it will continue to monitor. If possible, the sensorwill transmit its data to a dynamic treatment system designated as block1200. The treatment system receives the data at step 1210 and adjuststhe treatment at step 1230. The adjustment in treatment can be amechanical adjustment of a mechanical system or control of a therapeutictreatment system. In a further aspect, the system provides the patientor health care provider with a recommendation of adjusting the treatmentsystem. In this embodiment, the patient or health care providerconsiders the recommendation and instructs the dynamic treatment systemto make an adjustment in response to the indicated sensor signal.

The foregoing sensor systems have application to various skeletalprocedures and conditions, including but not limited to, limblengthening, artificial joints, natural joint repair, discectomy, neuraldecompression, bony defect repairs and bony fusions. It is contemplatedthat the disclosed sensor and corresponding dynamic treatment systemhave further applications throughout the skeletal system including thehip, knee, ankle, elbow and jaw joints and load bearing bones such asthe skull and long bones. Specifically, such disclosed sensors areuseful to evaluate tissue properties and detect changes to tissue in theskeletal system. It is contemplated that in another embodiment thesensor has a particular application with respect to detecting changes inbone density as it relates to osteoporosis. Further, in anotherembodiment the sensor is applied to detect tissue density changes withrespect to tissue around fixation implants, joint implants, or any othertype of implant. Moreover, an acoustic sensor may also be used to detectchanges in viscosity. Thus, the sensor may be utilized to listen forchanges in bodily systems and organs and alert healthcare professionalsto any impending or potential problems. These examples of potential usesfor the sensor are for example only and in no way limit the ways inwhich the current invention may be utilized.

Further, while the foregoing description has often described theexternal device as the means for displaying sensor data in humanintelligible form, it is fully contemplated that the sensor itself mayinclude components designed to display the data in a human intelligibleform. For example, it is fully contemplated that the sensor may includea portion disposed subdermally that emits a visible signal for certainapplications. Under one approach, the sensor might display a visiblesignal when it detects indicators indicative of conditions above thefirst threshold value. The sensor might also emit an audible sound inresponse to such indicators. In this sense, the sensor might act as analarm mechanism for not only detecting potential problems but alsoalerting the patient and doctor to the potential problems. This canfacilitate the early detection of problems. Under another approach, thesensor might display a different color visible signal depending on theindicators detected. For example, but without limitation, in the case ofmeasuring tissue density the sensor might emit a greenish light if theindicators detected by the signal indicate density is within the normalrange, a yellowish light if in a borderline range, or a red light if ina problematic range.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A system for treating a spinal segment within a patient, the systemcomprising a sensor having a sensing portion implantable in the bodyadjacent to the spinal segment, said sensing portion generating a sensorsignal in response to a sensed characteristic of the spinal segment; anda dynamic spinal treatment system having at least a first treatment modeand a second treatment mode, said treatment system in communication withsaid sensor and responsive to said sensor signal to adjust saidtreatment system from said first treatment mode to said second treatmentmode.
 2. The system of claim 1, wherein said dynamic spinal treatmentsystem includes a mechanical stabilization of the spine and said firsttreatment mode allows a first degree of motion in the spine and saidsecond treatment mode allows a second degree of motion in the spine. 3.The system of claim 2, wherein said first and second degrees of motioninclude compressive force along a longitudinal axis of the spine.
 4. Thesystem of claim 3, wherein said dynamic spinal treatment system isimplanted in the body adjacent the spinal segment.
 5. The system ofclaim 3, wherein said first degree of motion is greater than said seconddegree of motion.
 6. The system of claim 3, wherein in said seconddegree of motion is greater than said first degree of motion.
 7. Thesystem of claim 2, wherein the mechanical stabilization of the spinepermits rotation and said first and second degrees of motion includerotation of spinal segment.
 8. The system of claim 7, wherein saiddynamic spinal treatment system is implanted in the body adjacent thespinal segment.
 9. The system of claim 7, wherein said first degree ofmotion is greater than said second degree of motion.
 10. The system ofclaim 7, wherein in said second degree of motion is greater than saidfirst degree of motion.
 11. The system of claim 7, wherein said sensoris adapted to detect the instantaneous axis of rotation of the spinalsegment and said dynamic spinal treatment system adjusts between a firsttreatment mode with a first instantaneous axis of rotation and a secondtreatment mode with a second instantaneous axis of rotation.
 12. Thesystem of claim 1, wherein said dynamic spinal treatment system includesat least a first treatment compound.
 13. The system of claim 12, whereinsaid first treatment mode includes releasing said first treatmentcompound at a first concentration and said second treatment modeincludes releasing said first treatment compound at a secondconcentration.
 14. The system of claim 12, wherein said dynamic spinaltreatment system includes at least a second treatment compound, and saidfirst treatment mode includes releasing said first treatment compoundand said second treatment mode includes releasing said second treatmentcompound.
 15. The system of claim 14, wherein said dynamic spinaltreatment system includes a first reservoir with said first treatmentcompound and a second reservoir with said second treatment compound. 16.The system of claim 15, wherein said first treatment compound and saidsecond treatment compound are substantially the same material.
 17. Thesystem of claim 15, wherein said first treatment compound has a firstmaterial property and said second treatment compound has a secondmaterial property, said first material property different than saidsecond material property.
 18. A method of treating a spinal condition ina spinal segment of a human body, comprising: providing a sensorconfigured for implantation in the body adjacent a spinal segment and adynamic treatment system configured for communication with the sensor;implanting the sensor in the body adjacent a spinal segment; placing thedynamic treatment system in a first treatment mode; sensingcharacteristics of the spinal segment with the sensor; sending a sensorsignal to the dynamic treatment system; and adjusting the dynamictreatment system to a second treatment mode in response to the sensorsignal.
 19. The method of claim 18, wherein said dynamic treatmentsystem includes mechanical stabilization of the spinal segment and saidadjusting includes changing the stabilization of the spinal segment tothe second mode.
 20. The method of claim 18, wherein said dynamictreatment system includes a treatment compound and said adjustingincludes changing delivery of the treatment compound to the second mode.21. A system for treating a portion of a skeletal system within apatient, the system comprising a sensor having a sensing element with anouter housing, the outer housing including surface features for engaginga portion of the skeletal system to maintain a first position on theskeletal system, said sensing element generating a sensor signal inresponse to a sensed characteristic of the skeletal system; and adynamic treatment system having at least a first treatment mode and asecond treatment mode, said dynamic treatment system in communicationwith said sensor and responsive to said sensor signal to control saidtreatment system from said first treatment mode to said second treatmentmode.
 22. The system of claim 22, wherein said dynamic treatment systemincludes a mechanical stabilization device to stabilize a of the portionof the skeletal system and said first treatment mode allows a firstdegree of motion in the skeletal system and said second treatment modeallows a second degree of motion in the skeletal system.
 23. The systemof claim 22, wherein said first and second degrees of motion includecompressive force along a longitudinal axis of the portion of theskeletal system.
 24. The system of claim 23, wherein said dynamictreatment system is implanted in the body adjacent the portion of theskeletal system.
 25. The system of claim 21, wherein said dynamictreatment system is a lengthening intramedullary nail having a firstlength and a second length, said sensor sensing calcification of boneacross a fracture line and said intramedullary nail controlled betweensaid first length and said second length.
 26. The system of claim 22,wherein said mechanical stabilization device permits articulation of ajoint and said first and second degrees of motion include articulationof said joint.
 27. The system of claim 26, wherein said mechanicalstabilization device is an artificial knee.
 28. The system of claim 26,wherein said mechanical stabilization device is an artificial spinaldisc.
 29. The system of claim 21, wherein the dynamic treatment systemis a bone growth stimulator for electrically stimulating bone.
 30. Thesystem of claim 21, wherein said dynamic treatment system includes atleast a first treatment compound.
 31. The system of claim 30, whereinsaid first treatment mode includes releasing said first treatmentcompound at a first concentration and said second treatment modeincludes releasing said first treatment compound at a secondconcentration.
 32. The system of claim 30, wherein said dynamic spinaltreatment system includes at least a second treatment compound, and saidfirst treatment mode includes releasing said first treatment compoundand said second treatment mode includes releasing said second treatmentcompound.
 33. The system of claim 21, wherein said dynamic treatmentsystem includes a first reservoir with said first treatment compound anda second reservoir with said second treatment compound.
 34. The systemof claim 33, wherein said first treatment compound and said secondtreatment compound are substantially the same material.
 35. The systemof claim 33, wherein said first treatment compound has a first materialproperty and said second treatment compound has a second materialproperty, said first material property different than said secondmaterial property.